284 



DR E. G. COKER ON 



was 278 divisions. The specimen was then set in the tension grips of the Buckton 

 Testing Machine, and a gradually increased load applied, until a permanent set of - 18 

 inches was produced. Immediately after, a fresh test in torsion was made, the results 

 obtained being shown by col. II. The results are also plotted in fig. 26, from which 

 it will be seen that the effect of the tensional overstrain has entirely altered the pro- 

 perties of the material under torsion. The strain is no longer proportional to the stress ; 

 the deviation being even more marked than in the case of specimens upset by a previous 

 overstrain by torsion. 



Table VIII. — Steel Specimen. 



\ 



Diameter, 0"537". Length, 8 - 00". 12*75 divisions of scale = 1 min. of arc. 





Column I. 





Column II. 





No Tension. 





Specimen permanently lengthened 0"18 inch. 



Torque in 

 inch lbs. 



Reading. 



A 



Torque in 



inch lbs. 



Reading. 



A 











278 











299 



75 



278 



279 



75 



299 



301 



150 



557 



278 



150 



600 



321 



225 



835 



277 



225 



921 



339 



300 



1112 



277 



300 



1260 



364 



375 



1390 





375 



1624 



406 









450 



2030 



484 









525 



2514 



612 









600 



3126 



292 









525 



2834 



298 









450 



2536 



300 







i 



375 



2236 



300 









300 



1936 



305 









225 



1631 



310 









150 



1321 



311 









75 



1010 



310 













700 







